I don’t see what other health hazards there might be. Sure, the books are old and maybe well-used, but that’s true of libraries too and there is no hazard pay for librarians.
I looked for research on the health issues from used books and managed to find just one article on the risks of dust. It is not a scholarly article, includes no research, is not peer reviewed, and is on a website selling air monitoring and other safety equipment. I leave you to draw your own conclusions.
You’d be much more at risk as a teacher in a primary school. Small kids learn to cover their mouths with their hands when they cough and they then touch everything within reach. Now that is unhealthy.